Method and apparatus for retorting oil shale



Oct. 24, 1967 J. G. MITCHELL ETAL. 3,349,022 METHOD AND APPARATUS FOR RETORTING OIL SHALE I Filed June 23, 1965 //V Vf/V 7' 095 John 6 Michel! James H. Hoddad United States Patent Ofitice 3,349,022 Patented Oct. 24, 1967 3,349,022 METHOD AND APPARATUS FOR RETORTING OIL SHALE John G. Mitchell, Larchmont, and James H. Haddad,

Dobbs Ferry, N.Y., assignors to Mobil Oil Corporation, a corporation of New York Filed June 23, 1965, Ser. No. 466,384 9 Claims. (Cl. 20811) ABSTRACT OF THE DISCLOSURE A vertical gas combustion shale retort is described wherein a downwardly moving bed of shale granules is contacted with countercurrently rising gasiform material in a first multichambered open end spent shale cooling zone (recycle gas preheat zone), a combustion zone, a shale retorting zone and a shale preheating zone. The improvement of the above combination of steps resides particularly in the design and arrangement of the multichambered shale cooling zone to improve heat transfer therein and provide for more uniform heat exchange throughout the cross section of the retort between re cycle gas and spent shale particles contacted therein before passing the preheated recycle gas through the combustion section. In addition, the improvement resides in passing all gaseous material recovered from the combustion section of the retort to a zone for removal of solid particle fines before passing hot gases upwardly through the retorting Zone of the retort.

This invention relates to the method and means for retorting oil shale under conditions to recover shale oil. In a more particular aspect, the present invention relates to the method and means for improving the operating conditions within an oil shale retorting system to maximize the recovery of hydrocarbons from kerogen decomposition. In yet another aspect, the present invention relates to defining the method and means for retorting oil shale which permits a significant increase in shale throughputs without adversely aifecting the recovery of kerogen decomposition products thereform.

Shale oil technology as we know it today, has not reached an advanced commercially attractive stage and considerable work is yet to be done in developing a system of commercial acceptance for the economic recovery of valuable oil products. Oil shale is a sedimentary rock which contains a solid organic material known as kerogen. When this oil shale is heated to an elevated temperature, the kerogen is decomposed by pyrolysis to shale oil, gas and a carbonaceous residue.

One of the simplest systems for processing oil shale known today is a gas-combustion retort comprising four sections known as:

(l) a shale preheating section forming the upper part of the retort wherein the crushed shale of a granular size is introduced and brought up to retorting temperatures by direct heat exchange with a heat yielding fluid;

(2) a retorting section wherein the kerogen component of the shale is decomposed to shale oil vapors and shale oil vapors and shale gas;

(3) a combustion section wherein controlled combustion of the available combustable material is effected to provide at least a portion of the heat energy required in the retorting operation; and

(4) a shale cooling section wherein the spent shale particles are cooled to a desired low temperature suitable for handling while preheating at least a portion of the recycled gases separated from the shale decomposition products of the retorting operation.

In the system of the gas-combustion type herein discussed, crushed shale material of a particle size ranging from fines up to about three inch particles and hereinafter referred to as granular particle material, is passed down- Wardly through the zones comprising the retort as a relatively dense moving bed of granular material while recycle and other gases passed thereto move generally upwardly through the retort and countercurrent to the downwardly moving shale.

Some advantages of the above-discussed system are attributable to its simplicity, potentially large capacity and relatively efiicient utilization of heat made available therein and thereto. Accordingly, in an acceptable operation, the spent shale particles are cooled sufficiently in the retort to leave the retort at a relatively low temperature preferably below about 400 F. suitable for handling and disposal Without resorting to expensive heat resistant equipment. This heat exchange operation in the lower portion of the retort between the recycled gas and hot shale granules removed from the combustion section when properly effected, contribute measurably to the thermal efficiency of the process for the reasons more apparent from the following discussion.

It is an object of this invention to improve the operation of a gas combustion oil shale retort.

Another object of this invention is to more effectively utilize the heat available and supplied to a shale oil retort to optimize kerogen decomposition in the absence of particle fines.

A further object is to improve the recovery of decomposition products from oil shale for shale throughput rates greater than about 350 lbs. per hour per foot squared.

A still further object of this invention is to control the temperature profile of a gas combustion retort in a direction tending to maximize recovery of oil shale decomposition products.

Other objects and advantages of this invention will become more apparent to those skilled in the art from the following discussion. I

The present invention is concerned with improving the operation of a gas-combustion oil shale retort in a direction more commercially attractive and competitive than known methods. Furthermore, the present invention is concerned with the system and method of operation of a gas-combustion shale retort modified by mechanical innovations to significantly increase the recovery of desired kerogen decomposition products therefrom. More particularly, the present invention relates to a gas-combustion retort design and arrangement of apparatus which improves among other things the cross sectional temperature profile maintained in the retort shale preheat section, combustion sections, kerogen decomposition section, and shale cooling section therebelow. That is, operation of the shale cooling section is optimized to preheat to gaseous material passed upwardly therethrough countercurrent to the downwardly moving shale particles. This invention is further concerned with a gas-combustion retort design containing cross-sectional gasiform disengaging means above and substantially adjacent to the retort combustion section for removing gasiform material including hot gaseous combustion products along with any formed finely divided particle material so that the fines can be separated from hot gasiform material at an elevated temperature above the dew point of any entrained vaporous material. Thereafter, the gasiform material substantially free of fine particle material and at a temperature in the range of from about 700 F. to about 1200 F., and more usually from about 1000 F. to about 1100 F. is introduced into the kerogen decomposition section of the retort through a cross-sectional gasiform distributor means substantially intermediate the retort combustion section and a kerogen decomposition section thereabove.

Provisions may also be provided for removing fines from the crushed shale in the upper portion of the retort so that those fines can be removed from the retort separately from kerogen decomposition products.

By employment of the improved gas-combustion retort design of this invention in the manner hereindescribed, a significant increase in crushed shale and gas flow rates through the retort may be effected with advantage since refluxing of particle fines within the retort is substantially eliminated by their removal from the retorting system. Furthermore, higher gas flow rates are thereby permitted and this increase is then effectively employed in conjunction with a simultaneous increase in oil shale flow rate since the tendency for the retort to flood with condensed hydrocarbons in the upper part thereof is significantly reduced by the permitted increased gas flow rate passing upwardly through the retort.

It maybe saidtherefore, that the region of operability of a gas-combustion retort can be measurably improved by the method and means of the invention since (1) the shale flow rate may be significantly increased; (2) undesired fines refluxing and flooding conditions within the retort are virtually eliminated; (3) higher gasiform material flow rates can be employed without contributing to flooding conditions in the upper part of the retort and (4) a more uniform temperature profile across the retort can be achieved. Furthermore, the method of operation hereindescribed permits a preferred gas phase burning to the exclusion of substantial coke burning and little if any kerogen burning; a better temperature profile in the retort, more kerogen can be decomposed above the combustion zone; a high ,B.t.u..content off gas may be obtained and recovered from the retort and in addition more rigid spent shale particles will be present thereby significantly contributing to a reduction in producing dust or fines passing upwardly through the retort. Futhermore, by maintaining a more uniform cross-sectional temperature profile by the system and means of this invention, more efiicient use and recovery of available heat is possible thereby permitting the retort to operate under conditions minimizing carbonate decomposition and formation of fines.

In conjunction with the methodand means of this invention, a portion of uncondensable shale gas recovered from the retort product gasiform or vaporous material and separated from desired kerogen decomposition product is recycled to the retort. That is, a substantial portion of the separated product gas is recycled to a lower portion of the retort comprisingthe shale cooling zone for flow upwardly therethrough under conditions to preheat the recycled gas by countercurrent contact with downwardly moving hot shale particles, thereby cooling the shale particles to a temperature more suitable for handling upon withdrawal from the retort. Another portion of the recovered gas available for recycle to the retort may be employed as a dilution gas and seal gas. When recycle gas is combined with air and introduced into the combustion zone, it is employed as a heat carrier gasiform material to and from the combustion section of the retort. Furthermore, the dilution gas and air. mixture may be preheated directly or indirectly outside the retort, for example, by combustion with an inline burner or other suitable methods to raise the recycle gas temperature to a desired elevated temperature. The extent of gas heating employed in the method and means of this invention is preferably of an order of magnitude sufiiciently elevated so that upon introduction to the retort at substantially the inlet of the combustion section the temperature .profile of the recycled gaseous material passed upwardly from the bottom of the retort and heated by the descending shale particles will not be significantly reduced at the air inlets of the retort combustion section. Therefore, the introduced gasiform material must be of a heat carrying capacity and amount suflicientto be efiective in substantially limiting undesired burning and carbonate decomposition within the retort. Other gaseous material such as steam or flue gas which are considered relatively inert, in a process hereindescribed may be combined with the air and/ or dilution gas in desired quantities. In additiomthe volume of heat carrying gas comprising air and dilution gas passed to the combustion section may be varied considerably depending upon the method of heating employed and the volume may be in the range of from about 3000 up to, at least about 7000 or more standard cubic feet per ton of shale. That'is, when employing indirect heat'exchange means for heating the combustion supporting gas passed to the retort combustion section, use of volumes less than about 3500 per ton and as low as about 3000 s.c.f. per ton is sufiicient to provide the oxygen combustion supporting requirements of the retort. On the other hand, when partial combustion means are employed for directly heating the air either with or without. the presence of dilution gas a greater volume of air .is generally required and will be at least about 3500 s.c.f. per ton and more usually at least about 4000 s.c.f. per ton to: providethe oxygen combustion support requirements within the retort. Accordingly, it is important whether direct. or indirect heating exchange means are employed to limit the oxygen available for combustion within the retort to substantially combustion of gaseous material-to provide kerogen decomposition heat in the retort within the range of from about 300,000 B.t.u. per ton up to about 700,000 B.t.u. per ton. Therefore, the total heat supplied or available in the retort is limited by direct or indirect preheat of the combustion'supporting gases referred to as the sensible heat plus the potential heat from consuming oxygen within the retort and this combined heat input should be controlled withinthe range of from about 300,000 to about 700,000 B.t.u.s per ton ofshale.

Thus, by heating the gas streams in the manner herein discussed, the amount of air employed in the retort may. i

be varied over a considerably wide range of from about 2,000 to about 7,000 standard cubic feet per ton of shale,

so that a higher and desired mixed gas temperature is thereby attainable when the gas streams in the retort are combined adjacent the gas inlet of the combustion section. Having a higher mixed gas temperature means that the gases have a shorter distance to travel before the oxygen available in the gases is utilized to effect desired limited burning of available combustable material. Accordingly, more of the heat of retortin-g is supplied by the sensible heat in the gases rather than by heat of combustion on the surface of the shale particles. Thus, by supplying the gaseous material to the. retort in the manner above described, and used in combination with the method of operating the retort as hereindescribed, significantly more, kerogen decomposition products can be re-.

covered from the retort thereby significantly increasing the overall efliciency of the retort. Furthermore, lower peak shale temperatures will result thereby contributing to less carbonate decomposition and less fines production in the combustion section.

The apparatus forming the retort of this invention has been generally described above as one providing for improvements in heat transfer efliciency in the retort and particularly in the shale cooling section and recycle gas preheating section. Apparatus means are provided for the removal and recovery of fines from gaseous products at substantially the upper limit of the retort combustion section and for passing hot gaseous material substantially free of fines into the :kerogen decomposition section in theupper part of the retort above the combustion section. Accordingly, to improve the thermal profile of the retort the apparatus contains in an upper part of the shale cooling. section which extends downwardly from a lower part.

cross-section. This cross-sectional arrangement of elongated bafiles to form smaller open end elongated rectangular sections extends downwardly through the retort from substantially the lowest air distributor in the combustion section through the shale cooling zone to a section of the retort beneath the recycle gas inlet to confine the flow of shale particles through the plurality of elongated and vertically adjacent restricted passageways countercurrent to upfiowing recycle gas. These restricted elongated passageways are arranged to provide a predetermined pressure drop therein for the purpose of controlling the flow of gaseous material through any one section in a manner to be more uniform with the flow through another section. To aid with maintaining a more uniform pressure drop through any one section thus provided by the bafiies a recycle gas distributor manifold is arranged within the lower portion of the baffied section in a manner to form restricting orifices in each section through which the recycle gases must flow. These restricting orifices provide a major portion of the total bafiled section pressure drop. This means that regardless of the shale particle size and temperature conditions within each bafiled section, the flow of gas to each bafiled section will be substantially uniform thus providing for greater cooling stability in the overall shale cooling zone. In the lower part of the combustion section, a plurality of horizontal gaseous material distributor channels are provided in two horizontal planes vertically disposed from one another. These air distributor channels are also vertically staggered from one another so that combustion gases along with recycle gases moving upwardly through the retort for introduction to the combustion section will be substantially more uniformly distributed across the bed of shale particles. The gaseous material distributor channels provided in the combustion section and adjacent the lower end of the baffied cooling section more fully described herein are provided in the lower surface thereof with suitably sized orifice restrictions to obtain the desired air flow and distribution of gases into the shale particles in the area of the combustion zone.

In the arrangement of apparatus herein disclosed for retorting oil shale, there is provided a transverse chamber substantially intermediate the combustion section and the oil shale kerogen decomposition or retorting section. This intermediate transverse chamber referred to herein as a gaseous material distributor chamber, is formed in the upper part by a transverse baflle member provided with openings to form a grid member or a foraminous member suitable for flow of gaseous material therethrough. The lower part of the intermediate chamber is formed by a transverse bafile member impervious to the flow of gaseous material therethrough. The chamber thus formed by vertically displacing these bafile members from one another is vertically transversed by a plurality of adjacent spaced apart open end vertically disposed and elongated passageways or conduits of a size sufficiently large for the crushed shale particles to flow therethrough from the retorting section to the combustion section there-below. These elongated conduits or passageways extend sufiiciently below the lower bafiie member forming the intermediate gas distributor chamber to provide a gaseous material disengaging space between the lower baflie member and the upper bed surface of gravitating granular shale particles discharged from the bottom open end of the passageways. Gaseous material comprising gaseous products of combustion and any formed fines obtained from beneath the gaseous material disengaging space are removed therefrom at least in part and passed to one or more suitable fines separator equipment suitably positioned. In the method and apparatus of this invention, it is contemplated providing a valve controlled by-pass passageway or pipe about the fines removal separator chamber for flowing a desired amount of gaseous material from the combustion section directly into the retorting section. Therefore, substantially any desired portion of the gaseous material either partially or completely fines free may be passed directly to the dis tributor chamber without passing through the cyclone separator. Accordingly, in the specific arrangement of the drawing, the gaseous material at a temperature generally about 1000 F. is passed in substantially any desired quantity to one or more suitably positioned cyclone separators which may be positioned within or outside of the retort for removal of fines from the gaseous material. Therefore, it is contemplated locating a fines cyclone separator in the disengaging space provided by the conduit passageways between the upper level of the shale bed in the combustion section and the lower bafile member forming the distributor chamber.

The gaseous material removed from the combustion section either with or without additional heating thereof after removal of fines therefrom is returned by the intermediate gasiform material distributor chamber to the retort by flow through the upper foraminous bafile member thereof into the lower portion of the decomposition or retorting section. It is contemplated heating the gaseous material substantially free of any entrained fines by direct or indirect heat exchange means such as a line burner not shown. The gaseous material either with or without additional heating is passed through the upper foraminous or perforated grid member of the gas distributor chamber for flow upwardly through the descending shale particles in the retorting section in the absence of fines and under conditions to effect kerogen decomposition in the substantial absence of carbonate decomposition.

Having thus provided a general description of the improved method and means of this invention, reference is now had to the drawing by way of example which repre sents one cross-sectional arrangement in elevation of apparatus and a system for practicing the method of this invention.

At the top of the drawing, is provided an anti-segregation type bin 2 into which crushed shale of a granular particle size up to 2 or 3 inches are fed. One purpose of bin 2 is to substantially eliminate segregation of various sized particle materials formed during crushing of this shale and introduced into the retort so that a more uniform distribution of granular particle size material will be in the beds of shale therebelow. The granular shale particles pass downwardly as a relatively dense mass of particles through a confined conduit 4 separated into two seal gas zones 6 and 8. The purpose of these seal gas zones in conduit 4 is to prevent polluting the surrounding. atmospheric air with gaseous material from the retort and to prevent dilution of the recycle gas within the retort from seal air. Seal air is introduced to zone 6 by conduit 10 and recycle gas to zone 8 by conduit 12. A portion of the seal air goes up and through the antisegregation bin and the recycle gas goes down through the standpipe and into the retort as a seal media. The differential pressure between the two seal gas zones 6 and 8 and the recycle gas zone is essentially maintained at 0 inches of water. Standpipe 4 branches below seal zone 8 into a plurality of distributor conduits 14 for distributing shale across the retort cross section. The gas from the retort and oil mist formed therein is withdrawn by conduits 16 from a plenum chamber 18 about the standpipe 4 containing gas seal zones 6 and 8.

The granular shale particles distributed by conduits 14 form a relatively dense bed of particles 20 in the upper part of the retort defined by wall 22. The shale particles or granules moving down through standpipe 4 are thereafter passed through a number of anti-segregation distribution pipes 14. The purpose of these pipes or conduits being to prevent and inhibit segregation of various particle size materials introduced to the bed of solids therebelow.

' The bed of shale solids 20 is a section of the retort provided for accomplishing dual functions which include a mist or vapor cooling zone at least in the upper portion thereof wherein the vapors of the retorted oil are condensed into a mist and carried off with gasiform material comprising gaseous product of the combustion zone. Also in this zone or bed of solids, the shale particles become heated by hot gaseous combustion products in at least a lower portion thereof in an amount sufiicient to effect .kerogen decomposition in downwardly moving shale granules as a relatively compact bed by heating the shale particles in this zone to an elevated temperature in at least the lower portion of bed 20in the range of from about 700 F. to about 1000" F. A significant feature in the operation of' this upper zone containing the bed of solids 20 which is different from most gas combustion type retorts resides in prov-idng the 'hereindescribed means and method of operation by which we may eliminate solid particle fines from bed 20, so that condensation of vapors therein and formation of mist can take place in a substantially fines free shale bed.

It has been postulated that the particle fines are made for the most part in the zones below the kerogen decomposition zone and that the high temperature combustion zone therebelow is a major contributor of these fines. The fines or fine particle material formed in the lower portion of the retort flow upwardly into the kerogen decomponsition and condensing zone comprising bed 20 and elutriate themselves out of the bed. In order for these fines to pass out of the prior art retort systems, they must either go out the top of the retort with oil vapors or mist or they must cling to the downcoming wetted shale and/ or agglomerate with particle fines to form a larger particle agglomerate of fines with oil product. The particle agglomerates increase in size by refluxing in the retort until they attain a size sufficient to work their way down in a gas combustion retort with the shale granules into the highest temper-ature zone therebelowcomprising the combustion zone. In the combustion Zone the oil in the agglomerate is cracked, thereby significantly affecting efficient operation of the retort and contributing to losses in oil yield by forming coke particles. The refluxing of shale fines and fines produced by carbonate decomposition takes place with the small particles until the particle becomes large enough in size and mass to have sufificient weight to gravitate down through the retort into the high velocity combustion zone and in some instances eventually to the shale particle cooling zone.

To substantially eliminate this undesired condition and problem of fines refluxing in particularly the kerogen decomposition and condensing zone, a fines separator 24 is provided in conjunction with an intermediate plenum or gasiform material distributor chamber 26. Gaseous material moving upwardly through the retort and entraining solid fine particle material is separated from the downwardly moving shale granular material adjacent the combustion zone for treatment in separator zone 24 to remove solid fine particle material fromgaseous material before passing the gaseous material by conduit 28 into a suitable distributor chamber 26 across the retort substantially beneaththe kerogen decomposition zone. It is preferred to maintain the temperature of the gasiform material passed to separator zone 24 at a temperature above the dew point of vaporousmaterial passed thereto so that dust particles or solid fines particle material can be separated therefrom and removed from the bottom by conduit 30. The vaporous material substantially free of solid particle material or fines is passed by conduit 28 into plenum or distributor chamber 26 for redistribution of gasiform materialacross the lower cross section of bed 20.

Distributor 26 is traversed by a plurality of open end and substantially vertical conduits 32 which extend a substantial distance beneath baffle 34 to form a disengaging space 36 above a bed of solids 38. The upper baffle 40 of chamber 26 and V shaped in cross section is shown with a plurality of open end conduits 42 extending upwardly therefrom for flow of gaseous material therethrough and resembles in cross section a bubble cap tray.

The upper end of each conduit 42 is capped by a conical gas. distributor member 44. A by-pass conduit-46 con taining valve 48 is provided for passing a controlled amount of gasiform material directly from the disengaging zone 36 above the combustion zone to plenumvchamber 26 without passing through fines separator 24.

In a combustion zone below the disengaging zone and comprising a bed of granular shale particles 38, a plurality of combustion gas inlet channels 50 are provided, in the lower portion thereof at two levels and vertically staggered from one another so that .a more uniform distribution of oxygen containing combustion gas can be provided across the bed of particles. Providing for and maintaining substantial uniform distribution of combustion gases, across the cross sectional area of the bed of shale significantly improves the efliciency of the retort operation by reducing undesired localized peak temper ature conditions and clinkering of retorted shale in the combustion zone. To assist with maintaining desired distribution, the gasiform distributor channels are provided with restricting orifices in the lower surface area thereof for distributing combustion supporting gaseous material therethrough, and this arrangement in conjunction with the vertically staggered channels and other hereindescribed features of the retort help to obtain the desired distribution of gasiform material introduced to the lower portion of the combustion zone without unduly restricting the shale flow through the system.

Below the above-described staggered distribution channels 50 provided in the lower portion of the combustion sectionof the retort, there are provided a plurality of vertically spaced elongated baffles 52 arranged with respect to one another to divide the retort cross sectionally into a plurality of smaller elongated confined rectangular zones 54 adjacent one another through which shale granular material flows downwardly through countercurrently to rising gasiform material. Thus sub stantially cold recycle gas is passed upwardly through the elongated zones 54 abovedescribed and herein referred to as anti-channeling or channel retardation zones under conditions to heat the recycle gas and more uniformly cool the shale granules to a desired low temperature. This arrangement of bafiie-plates 52 forms elongated heat exchange compartments 54 which resembles in cross section a grid of relatively large rectangular openings. The arrangement of the baffles above described is provided to confine separate columns of shale granules in elongated confined heat exchange zones whereby the gas flowing counter currently therethrough is maintained at a more uniform desired flow rate substantially the same in each zone.

Cool recycle gas is introduced to the baffled heat exchange section through channel distributors 56 provided with restricting orifices in the lower surface. The channels 56 are located in the lower portion of the baffled se tion and arranged with respect to one another in each compartment or section thereof toprovide a cross section area of restricted flow and provide a predetermined pressure drop therein. The restricted sections formed by the channels and restricting orifices in the lower portion of the bafiied section is sufficient to provide a desired pressure drop in the bed of solids in any one elongated section. Therefore, within certain limits in every one of the baffle formed compartments or section of the heat exchange bed. For example, assuming that'one compartment or-section is operating at 2 inches of water pressure drop for a given gas mass velocity and another section is operating at 5 and the flow rate of gas can be controlled factors of 13 over or only 15%. Without restricting orifices the difference in gas flow in each section could be taken as the square root of the factors of 5 over 2 o 60%. It can be seen from this illustration that these restricting orifices, regardless of bed pressure drop relationships in the various zones due to particle size segregation or differences in temperature in the different sections of the bed, have a tendency to stabilize gas flow therethrough and temperature conditions encountered.

It is important to maintain a desired gas flow rate in each section and the bafiles 52 are extended a substantial distance beneath the restricting orifice sections of channels 56 and a distance sufiicient to prevent the recycle gas introduced by conduit 58 to the channels from readily short cutting around the baflles and going from one section into the bottom of an adjacent section.

The retort beneath the bafiied cooling zone is a channel draw off design arranged to provide substantial uniform draw off of granular material across the total cross section of the retort. A plurality of downcomers or standpipes 60 are provided in the lower portion of the retort beneath the shale cooling zone to accomplish this draw off. These standpipes or downcomers are arranged so that two or more discharge into an upper enlarged V shaped section of a lower standpipe until the plurality of separate stream withdrawn from across the bed of granular solids are converged to a single stream of particles confined within a V shaped zone in cross section defined by baffles 62. An oscillating or tilting table or vibrating feeder 64 is provided beneath an opening at the apeX of baifies 62 to control the flow of solids into a lower 1 chamber of the retort formed by Walls 66. This arrangement will permit use of a cluster of the above-described retort means in side by side relationship with respect to one another. In the lower portion of the solids withdrawal system is provided a pressure let down seal system within a standpipe 68 to which recycle gas and seal air or inert gas are supplied by conduits 70 and 72. This seal system is arranged so that only recycle gas introduced by conduit 70 will flow up into the retort and will not dilute the recycle gas passed to the cooling section of the retort with air introduced by conduit 72 to the seal unit. The air or inert gas flows downwardly with the retorted and cooled shale particles to reduce the pressure of the system. Any dust collected in the air 01 inert gas that is used in the seal zone goes down the leg 74 and is removed by an induced draft fan 76 by way of conduit 78 and a fines collecting cyclone 80. This gas free of dust fines, is then vented to the atmosphere by conduit 82.

Fines removed in cycle 80 are passed by dip leg 84 onto a conveyor belt 86 along with retorted shale particles deposited thereon from seal leg 74. The fines separated in cycle 24 are passed downwardly through a standpipe 30 to a level control chamber 90. The solids are then passed by a conduit 92 containing valve 94 operated by-level controller 96 onto the belt 86 for removal from the retort. The solids in standpipe 30 may be cooled in a suitable fine solid particle material cooling zone not shown before entering chamber 90.

Having thus provided a general description of the improved method and means of this invention, it is to be understood that no undue restrictions are to be imposed by reasons thereon except as defined by the following claims.

We claim:

1. In the retorting of oil shale granules by passage downwardly through a shale preheat zone, a kerogen decomposition zone, a combustion zone and a shale cooling zone countercurrent to rising gasiform material, the improvement which comprises cooling shale granules in said shale cooling zone by direct countercurrent contact with rising gasiform material in a plurality of elongated adjacently positioned confined passageways having a length to cross sectional ratio sufficient to maintain a substantially uniform gasiform material pressure drop through the separate passageways, recovering granular shale particles from said elongated passageways substantially uniform in temperature throughout the retort cross section, passing gasiform material preheated in said elongated passageway combined with combustion supporting gaseous material introduced to said retort upwardly through a combustion section countercurrent to downwardly flowing shale granules under conditions to heat said gaseous material by combustion, removing finely divided solid particle material moving upwardly through said mid r tort with said heated gasiform material in a fines removal zone adjacent the upper level of said combustion section, passing heated gasiform material substantially free of solid fines upwardly through the kerogen decomposition zone and recovering kerogen decomposition products and gasiform material from the upper portion of said retort.

2. A system for retorting crushed oil shale of non-uniform particle size which comprises distributing crushed shale particulate material of non-uniform size by an antisegregation device across the upper cross sectional area of a bed of shale particulate in the upper part of a gas-combustion retort vessel, causing the shale particulate material to gravitate downwardly as a dense mass of particulate through said shale retorting vessel comprising a shale preheating section, a shale decomposition section, a combustion section and a shale cooling section, said cooling section separated into a plurality of adjacently positioned elongated confined open end passageways of a length to maintain more uniform pressure drop in the separate passageways with one another when passing a cooling gas upwardly therethrough and countercurrent to downwardly gravitating granular particulate material, introducing cooling gas to the lower portion of each of said confined passageways for flow upwardly therethrough, introducing a combustion supporting gasiform material into the lower portion of said combustion section adjacent the open upper end of said elongated confined passageways, recovering gasiforrn material with entrained solid fines at an elevated temperature from said combustion section, removing entrained fines from said gasiform material, passing gasiform material substantially free of entrained fines upwardly through a bed of shale particulate material in said shale decomposition section under conditions to effect decomposition of kerogen in said oil shale particulate and recovering kerogen decomposition products from the upper portion of said retort vessel.

3. A method for retorting oil shale particulate material which comprises causing a mass of said particulate material to move continuously downwardly and countercurrent to upflowing gasiform material through a confined zone comprising an upper kerogen decomposition zone, and intermediate combustion zone and a lower cooling zone, maintaining a gasiform material distributor zone substantially intermediate said combustion zone and said decomposition Zone traversed by a plurality of elongated confined passageways for flow of particulate material therethrough, removing gasiform material from an upper portion of said combustion zone, separating any entrained finely divided solids from said removed gasiform material, passing gasiform substantially free of entrained solids into said distributor zone for distribution across the lower cross section of said decomposition zone, restricting the flow of particulate material downwardly in said cooling zone by a honeycomb of elongated confined passageways, causing gasiform material to move upwardly through said honeycomb of con-fined passageways into said combustion zone under conditions to effect desired cooling of said particulate material in said cooling zone and separately introducing to the lower portion of said combustion zone for flow upwardly therethrough combustion supporting gasiform material at a plurality of spaced intervals arranged to provide a temperature profile in said combustion zone relatively uniform throughout its cross section.

4. In the method of retorting oil shale particulate material in a gascombustion retort comprising a kerogen decomposition zone, a combustion zone and a shale cooling zone, the improvement which comprises, separating the cooling zone into a honeycomb of elongated open end passageways through which the shale particulate can flow downwardly countercurrent to gasiform material introduced to the lower portion of each of said passageways, passing gasiform material heated in said passageways into the lower cross section of said combustion zone, separately introducing combustion supporting gasiform material into the lower portion of said combustion zone at a plurality of spaced intervals arranged to provide substantially uniform distribution of gasiform materialthroughout the cross section of the combustion zone, removing heated gasiform material containing entrained fines from the upper portion of said combustion section, separating any entrained fines from said removed gasiform material, passing gasiform materials substantially free of entrained fines into a gaseous material distribution zone substantially intermediate said kerogen decomposition zone and said combustion zone, substantially uniformly distributing said gasitorm material at an elevated temperature across the lower cross section of said decomposition zone for flow upwardly therethrough under conditions to cause decomposition of kerogen in said decomposition zone and recovering kerogen decomposition products from the upper part of said oil shale retort.

5. A substantially vertical gas-combustion retort system comprising in combination, a hopper means in association with a standpipe ,for feeding crushed oil shale granules. into the upper portion of an oil shale retort, said standpipe arranged to include at least one seal chamber therein to which a suitable seal gas may be introduced, said standpipe terminating in a plurality of branched feed conduits for discharging shale particulate across the upper cross. section of a first bed of shale granules therebelow, said first bed of shale granules comprising a section of the retort system for heating the granules to a temperature sufficient to effect kerogen decomposition by direct heat exchange with hot gasiform material, a transverse gasiform material distributor chamber, across the retort separating said first bed from a lower second bed of shale granules, said distributor chamber traversed by a plurality of sub stantially vertical open end conduits through which shale granules flow from said first bed to said second bed, a vapor disengaging said second bed and said distributor chamber formed by said plurality of conduits, conduit means for passing gasiform material from said disengaging space to a solid fines separation vessel, conduit means for passing gasiform material substantially free of solid fines to said distributor chamber, a valved conduit communicating between said disengaging space and said distributor chamber, a plurality of vertically staggered substantially horizontal gasiform material distributor channels positioned in an intermediate portion of said second bed, said second bed beneath said channels separated by a plurality of substantially vertically positioned spaced apart batfie members arranged to form a plurality of side by side elongated open end passageways, channel. means coinciding with said baffle means in at least one horizontal direction for introducing gasiform material to the lower portion of each of said open. end passageways, a plurality of interrelated standpipes beneath said second bed for uniformly withdrawing shale particulate material from the total cross section of the second bed of shale for discharge into a single collector hopper, means for depressuring shale particles withdrawn from said single collector hopper, means for separating solid fines from gasiform material used during depressuring shale particles and standpipe means for rer moving solid fines separated from gasiformmate'rial employed in said retort system.

6. A method for retorting oil-shale particles in a gascombustion retort which comprises causing oil-shale parspace between the upper surface of ticles up to about three inches in diameter to move con- 1 tinuously downwardly through a gas-combustion retort as a substantially compact mass of granules, separating the mass of granules into an upper first bed from a lower second bed by a gasiform material distributor zone traversed by substantially vertical open end passageways extending beneath said distributor zone to form a gasiform material disengaging space above said lower bed, separating the lower portion of said lower bed into a plurality of adjacent elongated confined zones, passing gasiform material recovered from kerogen decomposition products upwardly through said adjacent adjacent confined zones under conditions to preheat said gasiform material to an elevated temperature, combining gasiform material thus preheated with combustion supporting gaseous material and further heating the gasiform material in the upper portion of the lower bed by combustion, disengaging solid fines from gasiform heated by combustion, passing heated gasiform material substantially free of solid fines into the lower portion of said upper bed, effecting decomposition of kerogen and preheating of the shale granules in said upper bed, recovering kerogen decomposition products and gasiform material from the upper part of the upper bed and employing gasiform material separated from desired kerogen decomposition products as the gasiform material and as.

part of the gaseous material above mentioned.

7. A method for retorting oil shale which comprises passing granular shale particles as a substantially compact mass of particles downwardly through a retorting zone comprising at least two separate beds of granular material separated by a gaseous material disengaging space and a gaseous material distribution zone extending across said retort zone, said beds of shale granules in communication with one another through a plurality of confined passageways suitable for flowing a dense mass of shale granules therethrough, passing gasiform material upwardly through the lower portion of said lower bed through segmented,

sections arranged to maintain a pressure drop in the segmented sections substantially equal while preheating said gasiform material to en elevated temperature suitable for introducing to a combustion section thereabove comprising an upper portion of said lower bed, adding a combustion supporting gas to said combustion section under conditions to effect combustion of gaseous material therein, recovering gasiform material heated to an elevated temperature in said combustion section, removing fines from at least a portion of said heated gasiform material, pass ing heated gasiform material substantially free of fines into said distribution zone, passing gasiform material at a suitable elevated temperature from said distribution zone upwardly through the upper bed of shale particles under conditions to efiect decomposition of kerogen in the shale particles and preheat the particles to decomposition temperatures, and recovering kerogen decomposition products along with gasiform material from the upper bed of shale granules.

8. A method for retorting oil shale which comprises gravitating a mass of shale granules continuously downwardly through at least two beds of shale granules sepai rated from one another by a gaseous material distribution sageways, separating entrained solid fines from said heated gasiform material, introducing gasiform material substantially free of entrained fines into the upper bed by way of said distribution zone under conditions to effect decomposition of kerogen in said shale granules and recovering kerogen decomposition products and gasiform material from said upper bed of shale granules.

9. A system for retorting shale granules which comprises gravitating a compact mass of shale granules downwardly through a retort comprising an upper bed of granules separated from a lower bed of granules by a gaseous material distributor chamber, said upper bed communicating with said lower bed through a plurality of open end conduits, the lower bed in at least its lower portion separated into a honeycomb of substantially vertical open end passageways, preheating gasiform material by countercurrent contact with shale granules in said passageways, further heating said preheated gasiform material to an elevated temperature in a combustion section above said passageways, removing solid fines from at least a portion of said heated gasiform material and thereafter passing the gasiform material at a desired elevated temperature into into said upper bed by said gaseous material distributor chamber, effecting kerogen decomposition in said upper bed with said heated gaseous material and recover- 1 4 ing kerogen decomposition material with gasiform material from the upper portion of the retort.

References Cited UNITED STATES PATENTS 2,774,726 12/ 1956 Eichna 20293 1,690,935 11/1928 Hubmann 201-34 2,519,342 8/1950 Berg 48-197 2,626,235 1/1953 Wilson 20134 2,661,325 12/1953 Savage 20134 2,812,288 11/1957 Lankford et a1. 20143 FOREIGN PATENTS 894,727 4/1962 Great Britain.

DANIEL E. WYMAN, Primary Examiner. P. E. KONOPKA, Assistant Examiner. 

1. IN THE RETORTING OF OIL SHALE GRANULES BY PASSAGE DOWNWARDLY THROUGH A SHALE PREHEAT ZONE, A KEROGEN DECOMPOSITION ZONE, A COMBUSTION ZONE AND A SHALE COOLING ZONE COUNTERCURRENT TO RISING GASIFORM MATERIAL, THE IMPROVEMENT WHICH COMPRISES COOLING SHALE GRANULES IN SAID SHALE COOLING ZONE BY DIRECT COUNTERCOURRENT CONTACT WITH RISING GASIFORM MATERIAL IN A PLURALITY OF ELONGATED ADJACENTLY POSITIONED CONFINED JPASSAGEWAYS HAVING A LENGTH TO CROSS SECTIONAL RATIO KSUFFICIENT TO MAINTAIN A SUBSTANTIALLY UNIFORM GASIFORM MATERIAL PRESSURE DROP THROUGH THE SEPARATE PASSAGEWAYS SUBSTANTIALLY UNIFORM IN TEMPERATURE THROUGHOUT THE RETORT CROSS SECTION, PASSING GASIFORM MATERIAL PREHEATED IN SAID ELONGATED PASSAGEWAY COMBINED WITH COMBUSTION SUPPORTING GASEOUS MATERIAL INTRODUCED TO SAID RETORT UNWARDLY THROUGH A COMBUSTION SECTION COUNTERCURRENT TO DOWNWARDLY FLOWING SHALE GRANULES UNDER CONDITIONS TO HEAT SAID GASEOUS MATERIAL BY COMBUSTION, REMOVING FINELY DIVIDED SOLID PARTICLE MATERIAL MOVING UPWARDLY THROUGH SAID MID RETORT WITH SAID HEATED GASIFORM MATERIAL IN A FINES REMOVAL ZONE ADJACENT THE UPPER LEVEL OF SAID COMBUSTION SECTION, PASSING HEATED GASIFORM MATERIAL SUBSTANTIALLY FREE OF SOLID FINES UPWARDLY THROUGH THE KEROGEN DECOMPOSITION ZONE AND RECOVERING KEROGEN DECOMPOSITION PRODUCTS AND GASIFORM MATERIAL FROM THE UPPER PORTION OF SAID RETORT. 